The invention concerns generally the technology of arranging data transmission between at least two terminals of a telecommunication system. Especially the invention concerns the technology of arranging for an optimally dimensioned channel solution for multimedia connections consisting of components characterised by various capacity needs.
Multimedia in general is understood as the synchronised presentation of audiovisual objects to a human user. At the priority date of this patent application it is expected that the concept of a conventional telephone call will evolve towards a point-to-point (or point-to-multipoint, or multipoint-to-multipoint) multimedia connection, in which each user has a terminal with audiovisual capabilities and the telecommunication system connecting the terminals will communicate various kinds of audiovisual material as well as plain digital data between the terminals. At the same time a clear tendency is seen towards more and more portable telecommunication terminals. A simple example of a portable multimedia terminal is a mobile video telephone, the user of which is able to view a video image of his conversation partner while listening him to talk. It is typical to multimedia connections that the amount of data to be transmitted may vary considerably according to which kind of imaging subsystems are used, what other data is there to be transmitted in addition to the video image, and what kind of data compression, encryption and channel coding schemes are employed.
Most mobile telecommunication systems are cellular radio systems by structure. The capacity bottleneck of the majority of them is the radio path between the mobile terminal and one or more fixed base stations, where time and bandwidth are scarce. Known telecommunication standards and proposals for standards are ill suited for the optimization of capacity usage on the radio path concerning multimedia connections, mostly because their channel allocation mechanisms are inflexible. For example the recommendation number H.324 of the ITU-T (International Telecommunication Unionxe2x80x94Telecommunication Standardization Sector) calls for the multiplexing of all different data streams (audio, video and data) into a single transmission channel, which has typically a capacity of 28.8 kbps and is provided through a modem according the V.34 standard or through a transparent HSCSD (High Speed Circuit Switched Data) transceiver in the GSM system (Global System for Mobile telecommunications). The capacity allocated for a single multimedia connection is therefore fixed, which dictates that if the demands of one component data stream increase, the other components must surrender some capacity. Even a minor increase in the amount of simultaneously transmitted data may cause considerable degradation in the quality of e.g. video images, which will in turn cause annoyance to the communicating parties.
The object of the present invention is to provide a method and arrangement for setting up and maintaining a multimedia connection that would allow for flexible changes in the amount of transmitted data per time unit and/or bandwidth. It is also an object of the invention to provide a method and arrangement for effectively using the resources of the radio interface between a mobile terminal and a base station for communicating information related to a multimedia connection.
The objects of the invention are achieved by a parallel arrangement of a real time channel and a non-real time packet channel which is closely associated to the real time channel.
The method according to the invention is characterised in that it comprises the steps of
directing the information related to real time service components through a radio transceiver, and between said radio transceiver and the local real time applications through a real time channel block and
directing the information related to non-real time service components through the same radio transceiver, and between said radio transceiver and the local non-real time applications through a non-real time channel block connected in parallel with said real time channel block.
The invention also applies to a wireless terminal arrangement for acting as a communicating party in a multimedia connection consisting of real time service components and non-real time service components, of which the real time service components are to be utilized by local real time applications and the non-real time service components are to be utilized by local non-real time applications. It is characterised in that it comprises
a radio transceiver capable of both circuit-switched and packet-switched operation,
a real time channel block for conveying the real time service components between the local real time applications and the radio transceiver and
a non-real time channel block, connected in parallel with said real time channel block, for conveying the non-real time service components between the local non-real time applications and the radio transceiver.
Additionally the invention applies to a telecommunication system which is characterised in that it comprises
a circuit-switched telecommunication network for conveying, between the terminals, information relating to real time service components and
a separate packet-switched telecommunication network for conveying, between the terminals information relating to non-real time service components parallelly with the information relating to the real time service components.
According to the invention a mobile multimedia terminal will comprise parallel arrangements for the communication of real time and non-real time information. Real time information is most advantageously related to audio and video, real time data and/or system control applications. Non-real time information may relate to any data the communication of which is not time-critical. Typical examples of non-real time information is the data representing a still image, a text file, a binary file or even low-bitrate commands like far end camera control commands.
To comply with existing standards it is advantageous to compose the parallel real time and non-real time arrangement of components that have been previously specified. At the time of filing this patent application a promising candidate for the real time part is a functionality according to the H.324 and GSM HSCSD standards, whereas GPRS (General Packet Radio Service) or even) SMS (Short Message Service) is suitable for implementing the non-real time part. The transceiver of the mobile terminal must be able to handle both the real time and non-real time part of the connection. Allowing for simultaneous activity by both parts is advantageous and can be realised for example with an HSCSD/GPRS GSM transceiver of Class A; however, a specific prioritizing arrangement may be applied if the transceiver is a HSCSD/GPRS GSM transceiver of Class B or other transceiver that only allows for one of the parts to be active at a given moment.
As a part of an advantageous embodiment of the invention, the usage of the radio resources is optimized by activating the required radio bearers only according to need. Therefore the multimedia connection according to the invention will not keep any radio resources unnecessarily reserved, which helps to avoid congestion in the radio access networks and saves electric energy which is important in portable battery-driven terminals. A user of a wireless terminal gains the advantage in the form of reduced communication costs, because the invention will enable the (generally more expensive) real time radio bearers to be involved only when they are necessary: non-real time services may be provided through (cheaper) non-real time radio bearers.